//
// Created by daiyizheng on 2022/3/27.
//

#include <vector>
using namespace std;
struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};

TreeNode* mergeTrees(TreeNode* root1, TreeNode* root2) {
    if(root1== nullptr)return root2;
if(root2==nullptr)return root1;
TreeNode *newNode = new TreeNode(root1->val+root2->val);

TreeNode *left = mergeTrees(root1->left, root2->left);
TreeNode *right = mergeTrees(root1->right, root2->right);

//回溯
newNode->left = left;
newNode->right = right;

return newNode;
}